Bryant Furnace Blower Running Constantly

GhostBuster · 11-27-2008, 10:39 PM

I have a Bryant SM-G furnace that is ancient - around 1971.
I have the fan on constantly for a day or so and discovered that the fan would no longer turn off. The heating still occurs to the set temp but the blower never shuts off. I wonder if the blower relay got stuck on. I have a Honeywell IAQ thermostat and went into test mode and shut off the blower and it did not stop. I then disconnected the heat and blower control wires from the control box and the motor did not shut off. Of course the motor does shut off if the switch on the furnace is flipped off.

So I am thinking it is a stuck blower relay in the furnace. I see bryant 821 on one place in the wiring and another relay inside the box attached to the 821 device.

Any thoughts what it is and the cost of the blower relay?

hoistdoctor · 11-27-2008, 10:55 PM

Do you have central air with this furnace?

GhostBuster · 11-27-2008, 11:06 PM

yep central air. I removed the heat, cool and blower wires from the honeywell control box and the blower did not stop.
I am looking at the scematic for the furnace right now.

hoistdoctor · 11-27-2008, 11:10 PM

Probably a green wire from the thermostat goes to the fan relay coil. When you select the fan to run and when you are calling for A/C, this wire picks up the fan relay which turns on the blower. Its probably got a stuck contact. Whack it with your screwdriver handle and see if it drops out.

GhostBuster · 11-27-2008, 11:17 PM

I bought this house almost 1 year ago and I still have a few days on the house warranty. For $100 deductible, I can have a repair person come out and fix it. I just wondered if the it is the relay if the cost is a lot for me to replace it. I am able to do so as I am trained in electrical stuff and troubleshooting.
I am just wondering if it is worth it for me to have the repair person come out.

hoistdoctor · 11-27-2008, 11:19 PM

The relay will cost you about $20.

hvaclover · 11-27-2008, 11:45 PM

Quote:

Originally Posted by hoistdoctor

The relay will cost you about $20.

RBM spst type relay if its a standard fan center

GhostBuster · 11-27-2008, 11:50 PM

Do I get it at the local HVAC store? Does Grainger have these?

GhostBuster · 11-28-2008, 12:17 AM

Thanks for the help. The "technical tap" turned it off. I went into test mode and the fan started again.
Is the fan relay the Model 821 relay? It has a sliding lever on it that off and max. I presume this is a time delay relay.

hoistdoctor · 11-28-2008, 08:41 PM

The 821 relay is wired parallel to the gas valve and it contains a small heater that warms up a warp switch inside to turn on the blower in heat mode. Since you have A/C, what is sticking is the relay that turns on the blower in A/C mode or switching it on with the thermostat. It could be made by RBM or others. You can get one from Grainger.

GhostBuster · 11-28-2008, 10:52 PM

So the 821 is the blower relay. I am looking at the schematic and the other relay is called the heat cool relay. Would that one be the I see that is an open frame relay? Should that one have the numbers written on it to help order another?

hoistdoctor · 11-29-2008, 09:46 PM

Does the wiring diagram show the power contact of this relay parallel to the 821 power contact?

#CARRIERMAN · 11-29-2008, 10:44 PM

Hi GhostBuster

On the 821 relay you will see a little pointer sticking out of on end of it. With the furnace plugged in if the blower keeps running. Take your finger and push this pointer to the left if the pointer is on to and to the right if its on the bottom. The blower should kick off. If it does you know for sure that this is your problem. The 821 relay is still available and is not all that exspensive. You could probably find it in one of these parts sites that are offered to you through this chatroom. I would not spend any more money on this furnace than you have to as it does not have much more life left in it. And you could afford to put a 90 plus Carrier in for what this thing cost you in gas for about two years.

Good luck
Rusty

GhostBuster · 11-30-2008, 01:07 AM

Quote:

Originally Posted by hoistdoctor

Does the wiring diagram show the power contact of this relay parallel to the 821 power contact?

The diagram shows heat cool relay with the coil hooked to the green wire. The NC contact of the heat cool relay goes to the contact on the blower relay which then goes to the medium high blower motor lead. The CO contact goes directly to the high speed blower lead.

GhostBuster · 11-30-2008, 01:10 AM

Quote:

Originally Posted by #CARRIERMAN

Hi GhostBuster

On the 821 relay you will see a little pointer sticking out of on end of it. With the furnace plugged in if the blower keeps running. Take your finger and push this pointer to the left if the pointer is on to and to the right if its on the bottom. The blower should kick off. If it does you know for sure that this is your problem. The 821 relay is still available and is not all that exspensive. You could probably find it in one of these parts sites that are offered to you through this chatroom. I would not spend any more money on this furnace than you have to as it does not have much more life left in it. And you could afford to put a 90 plus Carrier in for what this thing cost you in gas for about two years.

Good luck
Rusty

I saw that pointer and it sticks up. I did move it around and replace it into its place. Is this 821 relay the blower relay or the heat cool relay?